Not Completing Your Home Build with a Complete Upper Receiver? Here’s What You Need to Know  thumbnail image

Not Completing Your Home Build with a Complete Upper Receiver? Here’s What You Need to Know

5D Tactical - 23rd Jul 2021

For those of you thinking about taking on a home build project, there’s quite a bit you’re going to need to learn if you have no experience with gunsmithing. Luckily, there are a number of easy-to-use tools like lower jig kits you can use to streamline the process, and sellers like us at 5D Tactical sell build kits that make the process even easier, but all the same, you’ll need to make some choices.

For one, do you want to complete your home build using a completed upper receiver assembly or would you rather put together a stripped upper?

Benefits of Using a Stripped Upper instead of a Complete Upper Receiver Assembly

An AR-15 complete upper assembly is likely to come with a gas system, a forward assist, and ejection port door already installed. Complete AR-15 upper receivers also come with a barrel installed and torqued appropriately, as well as a handguard. If the complete upper receiver does not come with a BCG, CH, muzzle device, or buffer tube, you may be able to configure the package by adding them on - you can here at 5D Tactical.

By contrast, you can instead complete your build with a stripped upper receiver and customize it by tacking on the parts described above (and in detail below).

  • The draw of a custom build

Choosing to use a stripped upper instead of a complete assembly gives you the ability to customize every aspect of the rifle through the process. Choose a longer or shorter barrel, a modern, slim handguard, or a BCG with improved permanent dry lubricity since you’re starting with a blank slate.

  • Roll that experience into firearms maintenance

It’s impossible to assemble a firearm from parts without acquiring a certain level of intimacy about the process. Many gun owners, like many vehicle owners, are not particularly familiar with the operation of their equipment. Building one will enable you to develop familiarity with the operation of the platform; then later, when it’s time to make upgrades or repairs, you’ll know how to make them.

  • Circumvent shortages

Waiting for your gun shop to purchase an AR-15 in 5.56 NATO? That could be a long lead time, given the current supply chain issues and soaring demand on firearms - or you could simply build one yourself.

  • Enjoy the process

Another basic reason to go back to the basics and build a rifle with a stripper upper instead of a completed upper receiver is simply to enjoy the process.

Stripped Uppers: Billet Uppers vs. Mil-Spec Uppers

Once you take a step back and start looking for stripped uppers, you’re going to notice that some are considered mil-spec upper receivers and others are not.

For a stripped upper receiver to be considered mil-spec, it must be forged from 7075-T6 aluminum. Other receivers, often referred to as billet upper receivers, are made from either 6061-T6 or 7075-T6 aluminum, but instead of being forged, they are extruded in a billet and then CNC-machined.

All of our stripped mil-spec and billet upper receivers are manufactured according to the tightest tolerances and exhibit extremely high quality.

What Else You’ll Need:

If you’re completing your home build with a stripped upper instead of a completed upper assembly, here’s what you’ll need in order to “finish” the upper.

  • Barrel and Muzzle Device

Barrels are caliber specific and vary considerably in length as well, so this will affect handling and weight. In addition, some completed upper assemblies may come with muzzle devices but stripped uppers obviously don’t since they lack a barrel. You may want to configure your build with a muzzle brake or a flash hider.

  • Handguard

The handguard protects your barrel, your hands, and serves as a mounting point for attachments and accessories. If you’re looking to shed weight and increase the ergonomics of a rifle that would otherwise have a Picatinny quad rail, opt for a lighter modern alternative like a KeyMod or M-LOK rail. Both of these alternatives are light and tough.

  • Gas System (Gas Block and Gas Tube)

Your gas system enables the operation of the action, siphoning gas off from the barrel to the BCG. Make sure you choose a gas tube that fits your barrel and a gas block that fits your gas block journal. Also, slimmer profile gas blocks are generally favorable as they can more easily fit underneath slimmer profile handguards.

  • Bolt Carrier Group, Ejection Port Door, and Forward Assist

Most if not all stripped upper receivers do not come with an ejection port door, forward assist or bolt carrier group. You can opt for a classic, phosphate mil-spec BCG or go for a newer BCG with a modern nitride or nickel-boron coating that will exhibit greater permanent dry lubricity and will be easier to maintain.

  • Charging Handle

You’ll need a reliable charging handle to manually cycle your action and to clear jams. A stripped upper won’t come with one; you can choose a basic, no-frills charging handle or an ambidextrous model that ports the gas away from the shooter.

Lower Receiver, Lower Parts Kit, or a Complete Build Kit

In order to complete the build, you’ll also need an 80% lower receiver blank, a jig kit to complete the 80% lower, and a lower parts kit. You could also opt for a complete parts kit.

Start with either a complete upper receiver assembly or a stripped upper - whichever suits your project best. If you have any questions about your project or would like an expert’s opinion, please get in touch with us at 508-834-4223 or at